25.2 Fuse Bits
The ATmega16/32/64/M1/C1 has three Fuse bytes. Table 25-4 to Table 25-7 on page 257 describe briefly the functionality of
all the fuses and how they are mapped into the Fuse bytes. Note that the fuses are read as logical zero, “0”, if they are
programmed.
Table 25-4. Extended Fuse Byte
Extended Fuse Byte
-
Bit No
Description
-
Default Value
7
6
5
4
3
2
1
0
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
-
-
PSCRB
PSC reset behavior
PSCOUTnA reset value
PSCOUTnB reset value
Brown-out detector trigger level
Brown-out detector trigger level
Brown-out detector trigger level
PSCRVA
PSCRVB
BODLEVEL2(1)
BODLEVEL1(1)
BODLEVEL0(1)
Note:
1. See Table 7-2 on page 40 for BODLEVEL fuse decoding.
25.3 PSC Output Behavior during Reset
For external component safety reason, the state of PSC outputs during reset can be programmed by fuses PSCRB,
PSCARV and PSCBRV. These fuses are located in the extended fuse byte (see Table 25-4 on page 256).
If PSCRB fuse equals 1 (unprogrammed), all PSC outputs keep a standard port behavior. If PSC0RB fuse equals 0
(programmed), all PSC outputs are forced at reset to low level or high level according to PSCARV and PSCBRV fuse bits. In
this second case, the PSC outputs keep the forced state until POC register is written. Section 5.10.1 “Clock Prescaler
Register – CLKPR” on page 33
PSCARV (PSCOUTnA reset value) gives the state low or high which will be forced on PSCOUT0A, PSCOUT1A and
PSCOUT2A outputs when PSCRB is programmed. If PSCARV fuse equals 0 (programmed), the PSCOUT0A, PSCOUT1A
and PSCOUT2A outputs will be forced to high state. If PSCRV fuse equals 1 (unprogrammed), the PSCOUT0A, PSCOUT1A
and PSCOUT2A outputs will be forced to low state.
PSCBRV (PSCOUTnB Reset Value) gives the state low or high which will be forced on PSCOUT0B, PSCOUT1B and
PSCOUT2B outputs when PSCRB is programmed. If PSCBRV fuse equals 0 (programmed), the PSCOUT0B, PSCOUT1B
and PSCOUT2B outputs will be forced to high state. If PSCRV fuse equals 1 (unprogrammed), the PSCOUT0B, PSCOUT1B
and PSCOUT2B outputs will be forced to low state.
Table 25-5. PSC Output Behavior during and after Reset until POC Register is Written
PSCRB
PSCARV
X
PSCBRV
X
PSCOUTnA
Normal port
Forced low
Forced low
Forced high
Forced high
PSCOUTnB
Normal port
Forced low
Forced high
Forced low
Forced high
Unprogrammed
Programmed
Programmed
Programmed
Programmed
Unprogrammed
Unprogrammed
Programmed
Programmed
Unprogrammed
Programmed
Unprogrammed
Programmed
Brown-out detector
trigger level
BODLEVEL2(1)
BODLEVEL1(1)
BODLEVEL0(1)
2
1
0
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
Brown-out detector
trigger level
Brown-out detector
trigger level
256
ATmega16/32/64/M1/C1 [DATASHEET]
7647O–AVR–01/15
MICROCHIP [ MICROCHIP ]
